JP5332120B2 - Manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device that can prevent the separation of an enforcing sheet from an adhering surface in a semiconductor process subsequent to the bonding together of the surface of a semiconductor wafer and the enforcing sheet. <P>SOLUTION: In the semiconductor device manufacturing method after the surface side of a semiconductor substrate 1 is processed, a photoresist film 7 is coated for flattening surface roughness formed on the surface of the semiconductor substrate 1, and the back of the semiconductor substrate 1 is ground while the enforcing sheet 4 is bonded together to the flat surface of the photoresist film 7 via an adhesive agent 5. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device, which includes a step of attaching a reinforcing plate to a front surface side of a semiconductor substrate in order to protect and mechanically reinforce the front surface side of the semiconductor substrate when the back surface of the semiconductor substrate is ground.

A semiconductor substrate configured as a semiconductor device requires a required high resistance layer width that increases in proportion to the magnitude of the blocking voltage in order to ensure the blocking voltage (breakdown voltage). If the width of the high resistance layer is increased, the semiconductor substrate is correspondingly thickened. In the case of semiconductor silicon, the width of the high resistance layer necessary for the breakdown voltage is, for example, about 70 μm at 600 V and about 120 μm at 1200 V. On the other hand, in the semiconductor wafer process, if the thickness of the semiconductor wafer (semiconductor substrate) is thin, the number of wafer cracks in the process increases. However, if the thickness is 500 μm or more, crack defects in the wafer process are almost a problem. It is suppressed to the extent that it does not become. If the number of wafer cracks is large, not only does the defect rate increase and work efficiency deteriorates, but it is also not preferable from the viewpoint of cost. Therefore, it is preferable that the semiconductor wafer in the process is as thick as possible. Therefore, a thick wafer having a thickness of 500 μm or more is used at the time of introduction into the semiconductor wafer process regardless of the withstand voltage. However, if the wafer is thicker than the thickness required for withstand voltage (particularly in the high resistance layer), the voltage drop when an on-current is passed, that is, the on-resistance increases, In the wafer process, the process is performed on a thick wafer until the process on the front side of the semiconductor substrate is completed, and before the process on the back side of the semiconductor wafer is started, the back side of the semiconductor wafer is made to withstand pressure to reduce the on-resistance. There is a case where a manufacturing method of grinding to near a necessary thickness is employed. In such a manufacturing method, various semiconductor patterns and electrode films formed on the surface of the semiconductor wafer are protected and the reinforcing plate or film for the purpose of mechanically reinforcing the semiconductor wafer is bonded to each other after the back grinding step. The process is progressing. Bonding of the semiconductor wafer and the reinforcing plate or the reinforcing film at this time is generally performed via an adhesive or the like.
A conventional semiconductor device will be described. As shown in FIG. 3, the semiconductor silicon substrate 1 is finally subjected to processing steps (not shown) necessary for a semiconductor element function formed in the substrate 1, and finally. Semiconductor functional elements formed inside the semiconductor substrate 1 are connected and wired to metal electrodes and wiring metal 2 disposed on the surface. Further, a passivation film 3 such as a polyimide resin film is formed on the outermost surface as a protective film. However, the passivation film 3 is not formed so thick as to absorb all the steps (unevenness) resulting from the oxide film, the wiring metal 2 and the like being placed on the surface of the semiconductor substrate. Unevenness remains on the surface. The passivation film 3 is applied to the outermost surface of the semiconductor substrate, and then corresponds to a metal electrode portion for fixing an external connection lead wire such as an aluminum wire by bonding or a cutting separation line for dicing the semiconductor substrate into chips. Photolithography (photoetching) is performed to open a portion to be formed. As a result, the passivation film 3 is not a coating film as it is applied to the entire surface, but is a patterned film having a missing portion. In particular, the pattern of the cutting separation lines is formed in a lattice shape from end to end of the semiconductor substrate. In this state, for example, when a glass plate is attached as a reinforcing plate to the outermost surface of the passivation film 3 through an adhesive sheet, as shown in FIG. 4 (in FIG. 4, the semiconductor substrate 1 of FIG. 3 is inverted 180 degrees). A gap 6 or the like is always formed at the pasting interface. When the gap 6 is a gap corresponding to the above-described cutting separation line, as described above, the adhesive force of the pressure-sensitive adhesive sheet is deteriorated by the soaked gas or chemical solution, and the pressure-sensitive adhesive sheet is easily peeled off.

As a prior art, a process of bonding an adhesive sheet having an adhesive layer on one side of a base film to a semiconductor wafer surface having irregularities, a process of polishing the surface of the bonded base film, in that state, An invention relating to a semiconductor wafer grinding method including a step of grinding a semiconductor wafer back surface is known (Patent Document 1).
Furthermore, leaving the photoresist material used for pattern formation on the wafer surface as it is, grinding the back surface of the wafer with the surface protective adhesive sheet affixed thereon, then peeling the adhesive sheets, An invention of a manufacturing method of a semiconductor device in which a resist material is transferred to the pressure-sensitive adhesive sheets and removed from the wafer is known (Patent Document 2).
Japanese Patent Laying-Open No. 2005-19666 (Summary) JP 11-288907 A (summary)

  However, in various processes including grinding of the back surface side performed in a state where the adhesive sheet or the like is bonded to the front surface side of the semiconductor substrate as described above, when the substrate and the adhesive sheet are bonded, the semiconductor wafer surface side Gases and chemicals used in various processing processes on the back side are unavoidable in the gaps inevitably generated between the unevenness and patterned resist formed on the substrate and the adhesive sheet to be bonded. As a result, there is a problem that the adhesive strength of the pressure-sensitive adhesive sheet is deteriorated by the gas or chemical solution soaked and the pressure-sensitive adhesive sheet is peeled off, and the process stability is poor.

  Moreover, in the description of the above-mentioned patent document 1, when the surface of a semiconductor wafer and a base film are bonded together via an adhesive material, the surface of the base film is affected by irregularities on the semiconductor surface and has irregular irregular surfaces. It is intended to prevent adverse effects on wafer backside grinding accuracy, and is even suggested for the problem of peeling due to the gap between the base film and adhesive and the semiconductor wafer surface. It is not, and of course, no measures are taken and it is not solved at all.

  Furthermore, in the description of Patent Document 2 described above, a photoresist is further sandwiched between the wafer surfaces, a base film is further bonded through an adhesive, and the wafer back surface is ground. However, this photoresist is a patterned photoresist used for photoetching in the previous process, and naturally there is a part where the photoresist film is partially missing, so that there is sufficient clearance between the surface of the semiconductor wafer. It cannot be prevented. Therefore, the above-mentioned peeling problem of the base film cannot be sufficiently solved.

  The present invention has been made in view of the above points, and can prevent peeling from a bonding surface in a semiconductor process after bonding a semiconductor wafer surface and a reinforcing plate. It is an object of the present invention to provide a method for manufacturing a semiconductor device that does not deteriorate accuracy.

According to the invention described in claim 1, in order to flatten the unevenness formed on the surface of the semiconductor substrate by performing processing necessary for the function of the semiconductor element on the surface side of the semiconductor substrate. The back surface of the semiconductor substrate is ground by applying a photoresist and grinding the back surface of the semiconductor substrate in a state where a reinforcing plate is bonded to the flat surface of the dry photoresist film via an adhesive sheet attached to the surface. After the grinding is completed, the object of the present invention is achieved by removing the reinforcing plate by peeling the photoresist dry film using a photoresist stripping solution.

According to the second aspect of the present invention, after the processing necessary for the function of the semiconductor element is performed on the surface side of the semiconductor substrate, the plasma is formed in such a thickness that the unevenness formed on the surface of the semiconductor substrate is buried by this processing. A CVD oxide film is deposited, the oxide film is flattened by CMP, and the back surface of the semiconductor substrate is ground with a reinforcing plate attached to the surface of the oxide film via an adhesive sheet attached to the surface. It is preferable to provide a method for manufacturing a semiconductor device.
According to the invention of claim 3, the pressure-sensitive adhesive sheet is an ultraviolet curable pressure-sensitive adhesive sheet, and after the back surface grinding of the semiconductor substrate, the ultraviolet-curable pressure-sensitive adhesive sheet is irradiated with ultraviolet rays, The semiconductor device manufacturing method according to claim 2, wherein the reinforcing plate is removed together with the ultraviolet curable adhesive sheet.

According to the fourth aspect of the present invention in the claims, claim 2 or 3 maximum depth of the step of the flattened oxide film surface by the CMP is equal to or is 0.1μm or less It is preferable to use the method for manufacturing the semiconductor device.
According to the invention described in claim 5, the semiconductor substrate is semiconductor silicon, and the hard reinforcing plate is any one of a quartz plate, an inorganic glass plate, and an organic glass plate. Preferably, the method for manufacturing a semiconductor device according to any one of claims 1 to 4 is used.

  According to the present invention, since there is substantially no gap at the interface where the planarized surfaces are bonded together, the bonded interface is almost exposed to gases and chemicals used in various subsequent processing. Absent. Therefore, the adhesive force as it was when it was bonded is maintained, and a stable wafer process can be performed without being peeled until the intentionally bonded one is peeled off. Further, when a hard reinforcing plate such as a quartz plate or a glass plate is used for the reinforcing plate, the surface of the reinforcing plate is distorted due to the influence of stress, and the back surface grinding accuracy is not deteriorated.

  Embodiments according to a method for manufacturing a semiconductor device of the present invention will be described below with reference to FIGS. The present invention is not limited to the description of the examples described below.

  In the embodiment according to the present invention, as shown in FIG. 1, in order to perform a predetermined semiconductor device function on the surface side of the substrate 1 after adding processing steps necessary for a required semiconductor function to the inside of the semiconductor substrate 1. When a necessary process is performed, the surface of the semiconductor substrate 1 is formed by a step (not shown) due to a patterned oxide film, a step 2 due to a metal electrode, wiring, etc., a trench (not shown), and further a passivation film 3 or the like. Many irregularities are formed. Even on the surface of the semiconductor substrate 1 having such irregularities, if a photoresist photosensitive solution is applied, the recesses are filled with the photoresist solution, and the surface of the resist film 7 can be flattened. For example, a 120 cp (centipoise) negative resist is used as a photoresist to be used, and a spinner is applied at a rotational speed of 2500 rpm. A photoresist is buried in the concave portion of the surface of the semiconductor substrate 1 and dried at 90 ° C. for about 90 seconds. Then, a flat film with a thickness of 2 μm (at the time of drying) and a flat surface on the entire surface is formed. To do. As shown in FIG. 2, for surface protection and mechanical reinforcement of the semiconductor substrate 1 in the grinding process of the semiconductor substrate 1, which is a subsequent process (in FIG. 2, the front and back of the semiconductor substrate 1 of FIG. 1 are inverted 180 degrees). Then, an inorganic glass plate 4 having a thickness of about 500 μm was bonded using an adhesive (adhesive sheet) 5. In this way, according to the bonding of the inorganic glass plate 4 onto the surface of the flat photoresist film 7 having no recesses, the bonding is such that no gap is generated at the interface between the outermost surface of the semiconductor substrate 1 and the inorganic glass plate 4. Therefore, gas and chemicals used in various subsequent processes do not permeate the interface, and peeling from the bonded surface can be prevented.

  Thereafter, the rear surface of the semiconductor substrate is ground and polished to a predetermined thickness by CMP (chemical mechanical polishing apparatus). After the back grinding step is completed, the substrate is immersed in a photoresist stripping solution in order to remove the inorganic glass plate. When the photoresist is peeled off, the inorganic glass plate adhered thereon is also peeled off at the same time. After that, if a metal electrode film is deposited on the back surface through a necessary semiconductor processing step on the back surface side of the semiconductor substrate, a semiconductor substrate having the function of the target semiconductor device is completed.

  In this embodiment, by using a resist, it becomes possible to have functions of alkali resistance and acid resistance, and it is possible to prevent the gas and chemicals used at the time of processing from permeating and reducing the adhesive strength of the adhesive 5. .

  This embodiment differs from the first embodiment in that the photoresist film 7 is formed in the first embodiment but the TEOS oxide film 7 is formed in the present embodiment. The photoresist film has a problem in heat resistance, and cannot be used if there is a heat treatment process such as electrode annealing (about 400 ° C.) in the back surface process of the semiconductor substrate 1. Therefore, the plasma CVD oxide film is used when the back surface process of the semiconductor substrate 1 includes a heat treatment process.

  As shown in FIG. 1, a TEOS oxide film 7 is deposited with a film thickness that fills the unevenness by surface plasma CVD of an uneven semiconductor substrate 1, and the TEOS oxide film 7 is ground and planarized by CMP. In this embodiment, the TEOS oxide film is formed. However, an oxide film other than the TEOS oxide film may be used as long as it is an oxide film formed by plasma CVD. Since the plasma CVD oxide film can be formed at a low temperature (300 ° C. or less), it can be formed without affecting the semiconductor function formed on the surface side of the semiconductor substrate 1.

  Next, as shown in FIG. 2, the surface protection and mechanical properties of the semiconductor substrate 1 in the grinding process of the semiconductor substrate 1, which is a subsequent process (in FIG. 2, the front and back of the semiconductor substrate 1 of FIG. 1 are inverted 180 degrees). For reinforcement, an inorganic glass plate 4 having a thickness of about 500 μm was bonded using an adhesive (adhesive sheet) 5. The pressure-sensitive adhesive 5 may be made of a heat resistant material. In this example, an ultraviolet curable adhesive tape whose viscosity is weakened by ultraviolet irradiation was used.

  According to the bonding of the inorganic glass plate 4 on the surface of the flat TEOS oxide film 7, the bonding can be performed so that no gap is generated at the interface between the outermost surface of the semiconductor substrate 1 and the inorganic glass plate 4. Gases and chemicals used in various subsequent processes do not soak into the interface, and it is possible to prevent peeling from the bonded surface. Here, since the TEOS oxide film 7 has heat resistance as well as chemical resistance and gas resistance, the TEOS oxide film 7 can sufficiently maintain its function even if there is a heat treatment process at about 400 ° C. in the back surface process.

  Thereafter, the back surface of the semiconductor substrate 1 is ground and polished to a predetermined thickness by CMP. After the back grinding process was completed, in order to remove the inorganic glass plate 4, the adhesive 5 was irradiated with ultraviolet rays, and the inorganic glass plate 4 was removed together with the adhesive 5. The TEOS oxide film 7 can be used as a passivation film even if it is formed on the semiconductor substrate 1. Further, when the TEOS oxide film 7 is unnecessary, it can be easily removed by using hydrofluoric acid.

Thereafter, if a metal electrode film (not shown) is deposited on the back surface through a necessary semiconductor processing step on the back surface side of the semiconductor substrate 1, a semiconductor substrate having the function of the target semiconductor device is completed.
Next, an experiment was conducted on how the unevenness on the surface of the TEOS oxide film 7 before the inorganic glass plate 4 was bonded was affected.
After grinding the TEOS oxide film 7 using the CMP method until the maximum depth of the step becomes 0.01 μm, the TEOS oxide film 7 is dry etched to a width of 0.5 μm and a depth of 0.05 μm. A plurality of semiconductor substrates 1 formed with steps different from 0.1 μm and 0.15 μm were formed. Inorganic glass plates 4 were bonded to each other through adhesive 5 including those ground to 0.01 μm. Thereafter, it was immersed in buffered hydrofluoric acid for 10 minutes to check how much the TEOS oxide film 7 was etched. When the TEOS oxide film 7 is normally etched, the etching rate is 400 nm / min, and the solid film is etched by about 4 μm.

FIG. 5 is a diagram showing the influence of the step on the TEOS oxide film surface.
The result of measuring how the width of the formed step increases from the initial value of 0.5 μm is shown. As a result, it was found that the depth of the step hardly increased to 0.1 μm, and the width became wider when the depth of the step was 0.15 μm or more. This is considered to be a result obtained because buffered hydrofluoric acid flows into the step due to capillary action, but hardly flows when the depth is 0.1 μm or less.

Accordingly, it has been found that grinding by CMP may be performed until the maximum depth of the step on the surface of the TEOS oxide film 7 is 0.1 μm or less. When grinding so that the maximum depth of the step becomes 0.1 μm, the grinding time can be shortened compared to when grinding so that the maximum depth of the step becomes 0.01 μm.
In the above description, an inorganic glass plate is used as the mechanical reinforcing plate of the semiconductor substrate 1, but a quartz glass plate or an organic glass plate can also be used.

It is typical sectional drawing of the semiconductor substrate which shows the Example concerning the manufacturing method of the semiconductor device of this invention. It is typical sectional drawing of the semiconductor substrate which bonded together the reinforcement board which shows the Example concerning the manufacturing method of the semiconductor device of this invention. It is typical sectional drawing of the semiconductor substrate concerning the manufacturing method of the conventional semiconductor device. It is typical sectional drawing of the semiconductor substrate which bonded the reinforcement board concerning the conventional semiconductor device manufacturing method. It is a figure which shows the influence of the level | step difference of a TEOS oxide film surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Metal electrode, wiring metal part 3 Passivation film 4 Inorganic glass plate 5 Adhesive (adhesive sheet)
6 Gap 7 Photoresist film, TEOS oxide film.

Claims (5)

After processing necessary for the function of the semiconductor element on the surface side of the semiconductor substrate, a photoresist is applied to flatten the unevenness formed on the surface of the semiconductor substrate by this processing, and the flat surface of this photoresist dry film In addition, the back surface of the semiconductor substrate is ground in a state in which a reinforcing plate is bonded to the surface through an adhesive sheet that is pasted on the surface. After the back surface grinding of the semiconductor substrate is finished, the photoresist is removed using a photoresist stripping solution. A method of manufacturing a semiconductor device, wherein the reinforcing plate is removed by peeling a dry film. After processing necessary for the function of the semiconductor element on the surface side of the semiconductor substrate, a plasma CVD oxide film is deposited with a thickness that fills the irregularities formed on the surface of the semiconductor substrate by this processing, and this oxide film is planarized by CMP. A method for manufacturing a semiconductor device, comprising: grinding a back surface of the semiconductor substrate on a surface of the oxide film with a reinforcing plate bonded to the surface of the oxide film via an adhesive sheet attached to the surface. The pressure-sensitive adhesive sheet is an ultraviolet curable pressure-sensitive adhesive sheet,
3. The method of manufacturing a semiconductor device according to claim 2, wherein after the back surface grinding of the semiconductor substrate is finished, the ultraviolet curable adhesive sheet is irradiated with ultraviolet rays, and the reinforcing plate is removed together with the ultraviolet curable adhesive sheet. . 4. The method for manufacturing a semiconductor device according to claim 2 , wherein the maximum depth of the step on the surface of the oxide film flattened by the CMP is 0.1 [mu] m or less.   5. The semiconductor device manufacture according to claim 1, wherein the semiconductor substrate is semiconductor silicon, and the reinforcing plate is any one of a quartz plate, an inorganic glass plate, and an organic glass plate. Method.

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